The United States is a bit like a 375-pound, middle-aged man with a heart condition walking down a city street at night eating a Big Mac. He's sweating profusely because he's afraid he might get mugged. But the thing that's going to kill him is the burger.

Since the end of the Cold War, America has been on a relentless search for enemies. I don't mean a search in the sense of ferreting them out and defeating them. I mean that America seems to have a visceral need for them.